Energy accumulator and shock absorbing device for well pipe strings

ABSTRACT

A WELL TOOL COMPRISING TELESCOPICALLY ARRANGED TUBULAR MEMBERS CONNECTABLE IN A WELL STRING FOR RELATIVE LONGITUDINAL MOVEMENT BETWEEN EXTENDED AND CONTRACTED POSITIONS. A PISTON ON THE INNER TUBULAR MEMBER IS SEALABLY SLIDABLE WITHIN A CLOSED CHAMBER FORMED IN THE ANNULAR SPACE BETWEEN THE TUBULAR MEMBERS. THE PISTON HAS A CHECK VALVE WHICH PERMITS FLOW PAST THE PISTON UPON MOVEMENT IN THE CHAMBER IN ONE DIRECTION. A MEANS IS ALOS PROVIDED FOR RELIEVING EXCESSIVE PRESSURE IN THE CHAMBER UPON MOVEMENT OF THE PISTON IN THE OPPOSITE DIRECTION WITHIN THE CHAMBER.

Sept. 20, 1971 D. D. WEBB 3,606,297

- ENERGY ACCUMULATOR AND SHOCK ABSQRBING DEVICE FOR WELL PIPE STRINGS Filed Dec. 18, 1969 ATTORNEY! R W 5 W J /a d My 9 B a 0 A 7 c uzwfl aflwww fi a w \QH \\\i M. A/fii Zia. -v q H 5 3 w k m a United States Patent 3,606,297 ENERGY ACCUMULATOR AND SHOCK ABSORB- ING DEVICE FOR WELL PIPE STRINGS Derrel D. Webb, Houston, Tex., assignor to Houston Engineers, Inc., Houston, Tex. Filed Dec. 18, 1969, Ser. No. 886,221 Int. Cl. E21b 17/00; E21c 5/00, E16f 9/02 US. Cl. 267125 2 Claims ABSTRACT OF THE DISCLOSURE A well tool comprising telescopically arranged tubular members connectable in a well string for relative longitudinal movement between extended and contracted positions. A piston on the inner tubular member is sealably slidable within a closed chamber formed in the annular space between the tubular members. The piston has a check valve which permits flow past the piston upon movement in the chamber in one direction. A means is also provided for relieving excessive pressure in the chamber upon movement of the piston in the opposite direction within the chamber.

This invention relates to improvements in tools comprising telescopically arranged and relatively axially movable tubular parts adapted for connection as part of a well string disposed in a well bore and forming a closed chamber in which fluid is compressed by a piston on one such member, so as to accumulate energy therein, during the working stroke of the piston upon extension or contraction of the members in response to manipulation of the well string.

One such tool, which is shown and described in my prior Pat. No. 2,953,352, is adapted to be connected above an hydraulic jar in the string, so that, in response to an upward strain on the well string, energy is accumulated for supplementing the effect of the jar on the portion of the well string beneath such tool and then cushioning the effect of such jar on the portion of the well string above the tool. It has been found, however, that fluid compressed in chambers formed between relatively thin tubular members of tools of this type tends to leak past the piston in the chamber, especially when compressed to very high pressures. Eventually, the accumulation of fluid which thereby enters the chamber on the opposite side f the piston interferes with the return stroke of the piston. Although this fluid might eventually leak past the piston back to the chamber on the one side of the piston, this takes time and prevents full use of the tool on a frequent basis. Also, of course, there is a risk of damaging the tool by exceeding maximum allowable pressures during compression of fluid in the chamber.

It is therefore an object of this invention to provide a tool of this type in which there is little likelihood of leakage past the piston, but in which fluid which does leak past the piston may quickly return to the working side of the piston, whereby the tool will be ready for frequent use, and further in which pressures above the maximum allowed will be relieved during the working stroke of the tool.

These and other objects are accomplished, in accordance with the illustrated embodiment of the present invention, by a tool in which the piston on one of the telescopically arranged tubular members includes check valve means which permits flow past the piston during the return stroke of the one member. Thus, in a tool of the type shown in my prior Pat. No. 2,953,352, wherein energy is accumulated as the tubular members are moved toward extended position in response to an upward strain on the well string connected to the upper end of the one 3,606,297 Patented Sept. 20, 1971 ice member, the check valve means is operable to permit such flow, upon movement of the members toward contracted position, whereby they are quickly returned to such position and thus ready for repeated use.

More particularly, in the preferred embodiment of the invention, the piston is carried on the inner of the tubular members and includes axially spaced-apart flanges disposed therea'bout and a valve ring for shifting axially between seated positions on the oppositely facing sides of such flanges. The inner diameter of this valve ring is spaced from the outer diameter of the inner member, and the side of the flange on which the valve ring is seated during the return stroke of the first member is slotted so as to permit the aforementioned flow past the valve ring through the slots and the annular space between the valve ring and the inner tubular member.

The outer diameter of the valve ring is close to the chamber wall formed by the inner diameter of the outer tubular member, and a seal ring is carried in a groove in the outer diameter of the valve ring. This seal ring is maintained in sealing engagement against the chamber wall, even as the chamber expands under pressure, because fluid in the chamber on the working side of the piston acts over the side and inner diameter of the valve ring to stress it outwardly with a force which increases as its pressure increases. Even if some leakage Occurs, the check valve means permits the fluid to return to the working side of the piston upon the reutrn stroke of the inner member, as above described.

This tool also includes means for relieving excessive pressures in the chamber on the working side of the piston, which may occur due to overloading of the tool in the field. In the preferred embodiment of the invention, this means comprises conduit means in the inner member connecting with its exterior above and below the side of the flange on which the valve ring is seated during the working stroke of the tool, and relief valve means in the conduit for permitting flow from the working side of the piston to the other side thereof in response to a predetermined pressure in the chamber on the working side thereof.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is a longitudinal sectional view of a tool constructed in accordance with the present invention, and with the tubular members thereof in contracted position relative to one another;

FIG. 2 is an enlarged detail view of the part of the piston on the inner member of the tool indicated by the encircled portion of FIG. 1, during the Working stroke thereof;

FIG. 2A is a view similar to FIG. 2, but upon opening of the relief valve means;

FIG. 3 is also a view similar to FIG. 2, but during the return stroke of the tool; and

FIG. 4 is a cross-sectional view of the tool, on a scale intermediate that of FIGS. 1, 2 and 3, as seen along broken lines 4-4 of FIG. 2.

With reference now to a detailed description of the above-described drawings, the over-all tool shown in FIG. 1, and indicated in its entirety by reference character 10, includes an inner tubular member ill telescopically received within an outer tubular member 12 to provide an annular space between them. A box 13 on the upper end of the inner tubular member 11 provides a means for connecting it to an upper portion of a well string (not shown), and a pin 14 on the lower end of the outer tubular member 12 provides a means for connection to a lower portion of the well string. When the members are sealed with respect to one another, as will be described to follow, they provide a flow conduit forming a continuation of the well string flow conduit above and below.

The tubular members are longitudinally reciprocable with respect to one another between the contracted position of FIG. 1 and an extended position (not shown) in response to manipulation of the well string above the tool. As previously described, and as will be explained in more detail to follow, a tool of this type is normally connected in the well string above an hydraulic jar adapted to deliver a jar in an upward direction when an upward strain is taken on the string to extend the members 11 and 12.

The inner tubular member 11 is made up of an upper portion 11a which extends downwardly beneath the box 13, and a lower portion 1112 connected to the lower end of the upper portion 11a by means of a coupling 11c. The outer tubular member 12 includes an upper portion 12a connected to the upper end of an intermediate portion 12b, which in turn is threadedly connected to the upper end of a lower portion 120.

The upper portion of the inner tubular member 11 has longitudinal splines 15 thereabout which receive longitudinally extending pins 16 carried on the upper portion of the inner diameter of the upper end of the outer tubular member 12, so as to cause the inner and outer tubular members to rotate with one another and thus transmit torque from the upper portion of the well string to the lower portion thereof. More particularly, the pins 16 are received within slots formed in the upper end of upper tubular member portion 12a and are supported on abutments at the lower ends of such slots. The upper end of portion 12a includes a nut 17 which is removable to permit the pins 16 to be moved into and out of position within the slots.

The upper end of upper tubular member portion 11a beneath the head 13 is reduced to provide a downwardly shoulder 18 adapted to seat on the upper end of nut 17 in the contracted position of the tubular members. As above described, the tubular members are adapted to assume the contracted position when the tool is not being used to accumulate energy. Thus, the upper end of the nut 17 supports the inner tubular member in the well string thereabove in this inactive position of the tool.

The upper end of intermediate portion 12b of the outer tubular member 12 has a reduced inner diameter 20 which fits relatively closely about the outer diameter of lower portion 11b of the innertubular member 11 to support seal means 21 in position to form a sliding seal with the outer diameter of the inner tubular member. This seal means thus divides the annular space between the inner and outer tubular members into an upper spline chamber 22 and a lower compression chamber 23. For purposes of assembly, the coupling 110 is disposed within the spline chamber 22, and to prevent pressure build up within the spline chamber, ports 24 and 25 are formed in the upper portion 12a of the outer tubular member.

As will be understood from FIG. 1, the seal assembly 21 is of conventional construction and includes a seal ring 26 carried between a seat ring on its lower end and a gland nut on its upper end threadedly connected to the upper portion 12a of the tubular member.

The lower end of the pressure chamber 23 is closed by a seal assembly 27 carried on the reduced inner diameter 28 of the upper end of lower portion 12c of the outer tubular member for sealing about lower portion 11b of the inner tubular member. As shown in FIG. 1, this assembly includes a seal ring 29 and is of substantially the same conventional construction as the seal assembly 21. As will also be apparent from FIG. 1, the lower portion 11b of the inner tubular member is of such length that it will remain sealably slidable within the seal assembly 27 upon extension of the tubular members, and thus during operation of the tool to accumulate energy therein.

As also shown in FIG. 1, a piston 30 is carried on the lower portion 11b of the inner tubular member 11 for sealably sliding within the wall of the pressure chamber 23 formed by the inner diameter of the intermediate por tion 12b of the outer tubular member 12. More particularly, the piston 30 is located along an intermediate portion of the lower portion 1111 so as to be disposed in the lower end of the chamber 23 when the tubular members are contracted, whereby it has a maximum permissible stroke upon extension of the tubular members.

As also shown in FIG. 1, plugs 31 and 32 fill ports providing access to the pressure chamber 23' from the exterior of the tool. Thus, upon removal of the plugs, of course, a suitable fluid, such as an inert gas or a compressible liquid of some type, may be injected into the chamber.

The piston 30 includes a pair of spaced-apart upper and lower flanges 34 and 35, respectively, about the outer diameter of the tubular member .11, and a valve ring 36 axially movable between seated positions on the oppositely facing sides of the flanges. The inner diameter 37 of the valve ring is spaced radially outwardly from the outer diameter of the tubular member 11, and the outer diameter 38 of such ring is disposed close to the wall of the chamber formed by the inner diameter of outer tubular member 12. A seal ring 39 of suitable resilient material is carried in a groove in the outer diameter 38 of the valve ring to provide a sliding seal with the chamber wall.

The lower side of the valve ring and top side of flange 35 are parallel and provide continuous annular seating surfaces when the valve ring is in its lower position, as shown in FIG. 2. The top side of the valve ring and the bottom side of the flange 34 are aslo parallel to one another for seating engagement therebetween when the valve ring is in its upper position, as shown in FIG. 3. However, a plurality of radial grooves 40 are formed in the bottom side of the flange 34 so as to communicate the chamber above the valve ring with the space between the the inner diameter 37 thereof and the outer diameter of the inner tubular member 11, and thus with the chamber 23 on the lower side of the valve ring, when such ring is in its upper position, as shown in FIG. 3. Thus, the valve ring 36 and the oppositely facing sides of the flange against which it seats provide a one-way check valve means which prevents flow past the piston when the seat is in the lower position of FIG. 2, and the tubular members are being moved to extended positions, and permits flow past the piston from the upper portion of the pressure chamber to the lower portion thereof when the valve ring is in the upper position of FIG. 3, and the tubular members are being moved toward contracted position.

Consequently, when an upward strain is taken on the inner tubular member so as to raise the piston 30 within the pressure chamber, fluid on the upper portion thereof is compressed so as to accumulate energy therein. On the other hand, upon downward movement of the inner member 11, and thus during the return stroke of the piston, flow is permitted from the portion of the pressure chamber beneath the piston to the portion thereabove. This flow not only serves the purpose of accelerating the return stroke of the piston, and thus the return of the tool to a position for a further working stroke, but also permits fluid which may have bypassed the piston during its working stroke to return from the lower portion of the pressure chamber, into which it leaked, back up into the upper portion of the pressure chamber.

As will also be understood from FIGS. 2 and 3, with i the valve ring seated on the upper side of flange 35, the

high pressure fluid in the upper portion of the chamber 23 will act downwardly over the top side of the valve ring, as well as radially outwardly against the inner diameter 37 thereof. Consequently, the pressure fluid urges the outer diameter 38 of the valve ring toward the chamber wall with a force which increases as the piston moves upwardly in its working stroke. As a result, the outer diameter of the ring will be maintained close to the chamber wall inasmuch as the outward expansion of the outer diameter of the valve ring will compensate for expansion of the chamber wall due to the increased pressure.

As will also be apparent from FIGS. 2 and 3, the spacing of the inner diameter 37 of the valve ring outwardly from the outer diameter of the inner tubular member also facilitates assembly of the valve ring about the inner tubular member 11. Thus, as shown in FIGS. 2 and 3, the flange 34 comprises a separate ring connected to threads 41 about the outer diameter of the inner tubular member 11 which are of a smaller diameter than the inner diameter 37 of the valve ring, whereby the valve ring may be moved over the threads 41 during assembly and disassembly. The flange 35 may be integral with the inner tubular member, as shown.

The means for relieving excessive pressure in the upper portion of the chamber 23 during the working stroke of the piston comprise a conduit 42 within the inner tubular member 11 connecting at its upper end with the outer diameter thereon in the annular space between the flanges 34 and 35, and at its lower end with the exterior of the tubular member 11 below the top side of the flange 35. Preferably, the lower end of the conduit 42 extends outwardly so as to intersect with the outer side of the flange 35 generally intermediate its upper and lower ends, and an enlarged opening 43 connects an intermediate portion of the conduit 42 with the bottom side of the flange 35. A sleeve 44 is threadedly received in the opening 43 to mount a closure element 45 for movement therein between positions opening and closing the conduit 42.

Thus, as shown in FIGS. 2 and 3, the closure element 45 includes an enlarged head 46 guidably slidable within the sleeve 43 and a reduced stem extending upwardly from the end of the sleeve 44 and having a conical point for seating against a conical intersection of the opening 43 with the conduit 42 in the closed position (FIG. 2). A spring 48 is held within the sleeve by means of a pin 49 extending across the inner diameter of the sleeve for urging the closure member 45 to its closed position. However, the closure member is adapted to be urged away from seated position to open the conduit 42 (FIG. 2A) when the pressure in the upper portion of the chamber 23 reaches a predetermined level. When the conduit 42 is thus opened, excessive pressure in the chamber 23 is relieved through the slots 40, the annular space inside the valve ring, and the conduit 42 into the lower portion of the pressure chamber beneath the piston 30.

In the aforementioned use of the tool 10, it is connected in a well string above an hydraulic jar, which may be of the construction shown in US. Pat. No. 2,802,703. In the event the string becomes stuck in the well bore beneath the jar, the operator lifts the string to take an upward strain on it. This raises the piston of the tool 10 as well as a piston on the inner tubular member of the jar and, due to resistance of each piston to lifting, stretches the string as pressure builds up in the chamber of each tool above its piston.

When the piston of the jar moves into an enlarged portion of its chamber, the stretch in the string causes the inner member to move rapidly upwardly, at which time a shoulder thereon engages with considerable force a shoulder on the outer tubular member, which is connected to the struck portion of the string. The energy accumulated in the tool 10 supplements that stored in the well string to add to the force of impact. It also cushions the downward reaction on the inner tubular member of the jar to absorb shock therefrom which might otherwise be transmitted to the string above the tool.

Obviously, more than one such jarring operation may be required to release the struck string. The construction of the tool 10 is particularly useful in permitting it to quickly return to its fully retracted position for this purpose.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein'set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1s:

1. A tool adapted for connection as part of a string of pipe to be disposed in a well bore, comprising first and second tubular members telescopically arranged with respect to one another to provide an annular space therebetween and being movable longitudinally relatively to one another between extended and contracted positions, means on one end of each member for connecting the opposite ends of said tool in said well string, means on said members forming sliding seals with one another to provide a closed annular chamber within said annular space, said first member having a piston Within the chamher for compressing fluid within the chamber on one side of the piston as the members move in one longitudinal direction relative to one another, said piston including axially spaced-apart flanges about the first member, a valve ring disposed about said first member for shifting axially between seated positions on each of said flanges, the inner diameter of said valve ring being spaced from the outer diameter of said first member and the outer diameter of said rigid ring being close to the chamber wall, a seal ring .carried in a groove in the outer diameter of the valve ring for sealing against the second member, said valve ring being stressed outwardly by compressed fluid in said chamber to normally maintain the outer diameter thereof close to said chamber wall despite outward expansion of said chamber, and one of one side of the ring and the flange on which said one side seats being slotted to permit flow therethrough when said one side is seated thereon upon relative longitudinal movement of said members in the opposite direction, and pressure relief valve means permitting flow from said one side of the piston to the said other side thereof in response to a predetermined pressure of fluid in said chamber on said one side upon relative movement of said members in said one direction.

2. A well tool of the character defined in claim 1, wherein said pressure relief valve means includes conduit means in said first member connecting with the exterior thereof above and below the seal ring as said members are extended, and valve means in said conduit permitting said flow from said one side to said other side of the piston.

References Cited UNITED STATES PATENTS 2,712,435 7/1955 Allen 267-137 2,802,703 8/1957 Harrison 297 2,953,352 9/1960 Webb 267-71 3,311,180 3/1967 Gilreath et al. 6423X 3,350,900 11/1967 Harrison 64-23 ARTHUR L. LA POINT, Primary Examiner H. BELTRAN, Assistant Examiner U.S. C1.X.R. 

